Proliferative Glomerulonephritis with Monoclonal Immunoglobulin G Lambda Deposits: Report of the First Pediatric Case

Abstract

Proliferative glomerulonephritis with monoclonal immunoglobulin G deposits (PGNMID) is a recently described, uncommon renal disorder which is considered a monoclonal gammopathy of renal significance. Although some patients will have a detectable monoclonal spike, overt hematologic malignancy is found in only a minority. Most patients with PGNMID are over the age of 50 years, and to our knowledge no cases have been reported in children or adolescents. Renal biopsy shows variable histologic patterns by light microscopy, with membranoproliferative and membranous patterns being most common. Immunofluorescence microscopy demonstrates restriction to a single immunoglobulin G heavy chain isotype and a single light chain subtype. Electron microscopy reveals granular, unorganized deposits. We report a rare pediatric case which occurred in a 17-year-old female. The rarity of this entity in the adult population has not permitted a standard treatment regimen to be established. Our adolescent patient was treated with multiple treatment regimens including prednisone, mycophenolate mofetil, rituximab, bortezomib, and daratumumab. Our case demonstrates that awareness of this disorder by pediatric nephrologists and pathologists is vital to guide accurate disease classification, prognosis, and treatment.

Keywords: Glomerulonephritis; Immunoglobulin G; Monoclonal immunoglobulins.

Fig. 1.

Kidney biopsy findings. a Light microscopy shows a glomerulus with basement membrane double contours (arrows) and endocapillary hypercellularity. Periodic acid-Schiff stain; original magnification ×400. b Immunofluorescence microscopy shows strong (4+), granular glomerular capillary wall and mesangial staining by lambda. Original magnification ×400. c Immunofluorescence microscopy shows strong (4+), granular glomerular capillary wall and mesangial staining by IgG3. Original magnification ×400. d Electron microscopy shows subepithelial (white arrow), subendothelial (blue arrow), and mesangial (red arrow) granular electron-dense deposits, some with a variegated appearance. Original magnification ×1,500.